DESCRIPTION (adapted from the application) The long-term goals of the applicant's research program will test the following two hypotheses: 1) that the podocyte (glomerular visceral epithelial cell) is required for glomerular angiogenesis during development and 2) that the podocyte is pivotal in progression of chronic renal dysfunction due to a variety of underlying causes that include diabetes, aging and inflammation. The promoter of a podocyte-specific gene, nephrin, has been cloned. A transgene containing 1.25-kb of the 5' flanking region of the human nephrin gene recapitulates the endogenous expression of the nephrin mRNA transcript, and is only expressed in podocytes in capillary-loop and mature stage glomeruli of the developing murine kidney. The proposed studies will use this promoter to generate novel reagents to delineate the role of the podocyte in kidney development and disease. The main objective of the present application is to develop mouse model systems to manipulate podocyte gene expression in vitro and in vivo. The Specific Aims include: 1. To generate a podocyte-specific Cre-recombinase mouse line in order to delete and over-express genes in a cell-specific manner during renal development. 2. To generate mouse founder lines that can be used to modify gene activity in an inducible manner in podocytes. 3. To isolate novel murine podocyte cell lines that expresses a "living" marker of differentiation. 4. To further characterize the cis-acting elements within the 1.25-kb podocyte-specific promoter of the nephrin gene in order to identify trans-acting factors that are responsible for podocyte-specific expression. 5. To generate a podocyte-specific knockout of vascular endothelial growth factor (VEGF). The reagents generated in the present application will allow both temporal and spatial modification of gene activity specifically in podocytes. It will be possible to manipulate candidate genes involved in glomerular angiogenesis and to determine the role of the podocyte in setting up the glomerular filtration barrier. In future studies, these reagents will be useful to determine the role of the podocyte in glomerulosclerosis and ultimately, to identify therapeutic targets for chronic renal disease.